The present invention relates to a positive resist composition used for lithographic printing plates, semiconductor production processes, such as IC, etc., productions of circuit substrates for liquid crystals, thermal heads, etc., and further other photofabrication processes. Particularly, the positive photoresist composition of the invention functions by high-energy radiations such as far-ultraviolet rays (including excimer laser light, etc.), electron rays, X-rays, and radiations, and are suitably used for the production of semiconductor integrated circuits.
Hitherto, in the production processes of IC, LSI, etc., fine working by a lithography using a photoresist composition has been carried out. Recently, with the high-integration of integrated circuits, the formation of hyperfine patterns of a sub-micron region and a quarter micron region has been required. With the requirement, the light-exposure wavelength tends to become shorter wavelength such as from g line to i line and further an excimer laser light. At present, a lithography using an excimer laser light has become the important working technique in the field, and a resist suitable for such an excimer laser lithographic process, a chemically amplified type resist has been employed.
The chemically amplified type resist composition is a material of forming an acid at the exposed portions by the irradiation of radiations such as a far-ultraviolet light, etc., and by changing the solubility of the irradiated portions by the active radiation and the non-exposed portions in a developer by the reaction using the acid as a catalyst, patterns are formed on a substrate. The chemical amplified type resist has the advantages of having a high resistance and a high resolution, and capable of forming images by a compound generating an acid by the irradiation of small amount of radiations (hereinafter, the compound is referred to as xe2x80x9cphotoacid generatorxe2x80x9d).
The above-described chemically amplified resist can be largely classified into (1) a three-component system made of an alkali-soluble resin, a photoacid generator, and a dissolution-inhibiting compound to the alkali-soluble resin and having an acid-decomposing group, (2) a two-component system made of a resin having a group, which becomes alkali soluble by being decomposed by the reaction acid, and a photoacid generator, and (3) a hybrid system made of a resin having a group, which becomes alkali soluble by being decomposed by the reaction acid, a low-molecular dissolution inhibiting compound having an acid decomposing group, and a photoacid generator. In these positive-working chemically amplified resists of the two-component system, the three-component system, and the hybrid system, an acid is generated from the photoacid generator by light exposure, and after heat treatment, by developing, resist patterns are obtained.
In the lithography using the chemically amplified type resist, a photoresist excellent in the characteristics such as the sensitivity, the resolution, the profile, the coating property, the dry etching resistance, the adhesion, the substrate dependence, the stability to the environment (for example, the resist dimensional stability by the fluctuation of the setting time of the resist), the depth of focus (for example, the pattern forming property to the focus gap at the irradiation of radiation), etc., has been demanded and many means for improving the performances by additives have hitherto been proposed.
Because the chemically amplified resists has the specific reaction mechanism, it has been attempted to improve the resist characteristics, particularly the environmental stability by preventing the diffusing property of the generated acid by adding an acid scavenger. For example, it is proposed to add organic amines as disclosed in Japanese Patent Laid-Open Nos. 127369/1993, 232706/1993, 249662/1993, 289322/1993, 317902/1994, 92678/1995, 120929/1995, etc. However, there is a problem that when an amine is added, the resolution is improved but the sensitivity is lowered.
On the other hand, it has been attempted to add various kinds of compounds to the chemically amplified resist composition for the purposes of improving the sensitivity, the improvement of the resist pattern forms. For example, it is disclosed to add carboxylic acids in Japanese Patent Laid-Open Nos. 181279/1993, 92679/1995, 6002/1994, and 6003/1997, U.S. Pat. Nos. 5,955,240 and 5,948,589, European Patent 67951, etc.; it is disclosed to add aromatic polyhydroxy compounds in Japanese Patent Laid-Open Nos. 134345/1992, 217251/1992, 181680/1995, and 211597/1996, U.S. Pat. Nos. 5,688,628 and 5,972,559, etc.; and it is disclosed to add sulfonamide compounds in Japanese Patent Laid-Open Nos. 181263/1993 and 92680/1995.
Furthermore, means for improving the resist characteristics such as the resolution, the light exposure latitude, the adhesion, the substrate dependence, etc., has been provided. For example, the methods of preventing the occurrence of pattern collapsing by the addition of formamide or acetamide compounds are disclosed in Japanese Patent Laid-Open No. 5987/1997, U.S. Pat. No. 5,770,343, and European Patent 749044 and it is disclosed to improve the substrate dependence by adding nitrogen-containing compounds such as succinic acid imide, phthalimide, etc., in Japanese Patent Laid-Open No. 44950/1999. Also, the methods of improving the stability to the environment (for example, the resist dimensional stability by the fluctuation of the setting time of the resist), the resolution, the depth of focus, etc., by the addition of the compounds (photobases) lowering the basic property by light exposure are disclosed in Japanese Patent Laid-Open Nos. 232706/1993, 11835/1994, 242606/1994, 266100/1994, 333851/1995, and 333844/1995, U.S. Pat. No. 5,663,035, and European Patent 677788.
Furthermore, it is disclosed in Japanese Patent Laid-Open No. 297396/1997 to improve the resolution and the depth of focus by adding a specific low-molecular acid-decomposing dissolution-inhibiting compound to a two-component type chemically amplified resist.
However, in the photoresist composition for fat-ultraviolet light exposure, even by the techniques as described above, about the performance of a line edge roughness, there are many unsufficient points, and thus the improvement has been required. In this case, the line edge roughness is that the edges of the interface between the line pattern of a resist and a substrate fluctuates irregularly to the direction perpendicular to the line direction because of the characteristics of the resist. When the pattern is observed from right above, the edge is seen as roughness. The roughness is transferred by the etching step using the resist as a mask to deteriorate the electric characteristics, whereby the yield is lowered.
Particularly, with the resist pattern size becomes a quarter micron or smaller, the requirement of improving the line roughness has been increased but the guideline for the improvement has not yet been disclosed.
As described above, because in the known techniques of the photoresist compositions, a roughness is seen on the edge of a pattern and stable patterns are not obtained, a further improvement has been desired.
Accordingly, an object of the invention is to provide a positive resist composition capable of giving an excellent resist pattern profile wherein the edge roughness of the pattern is improved and a development defect is also improved.
As the result of intensive investigations on the materials constituting a resist composition in the positive-working amplified system, the present inventors have found that the above-described object can be attained by using a specific nitrogen-containing compound and have accomplished the present invention.
That is, the above-described object can be attained by the constitutions of the invention described below.
(1) A positive resist composition comprising:
(A) a resin having an aliphatic cyclic hydrocarbon group and increasing the solubility to an alkali developer by the action of an acid;
(B) a compound generating an acid upon irradiation with one of an actinic ray and radiation; and
(C) a nitrogen-containing compound having in the molecule at least one partial structure represented by formula (I): 
(2) The positive resist composition according to item (1), wherein the resin (A) comprises at least one selected from the group consisted of: a repeating unit having a partial structure containing an alicyclic hydrocarbon, represented by formula (pI) to (pVI) below; and a repeating unit represented by formula (II) below: 
wherein R11 represents a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, or a sec-butyl group; Z represents an atomic group necessary for forming an alicyclic hydrocarbon group together with the carbon atom; R12 to R16 each independently represents a straight chain or branched alkyl group having from 1 to 4 carbon atoms or an alicyclic hydrocarbon group, wherein at least one of R12 to R14 or one of R15 and R16 represents an alicyclic hydrocarbon group; R17 to R21 each independently represents a hydrogen atom, a straight chain or branched alkyl group having from 1 to 4 carbon atoms or an alicyclic hydrocarbon group, wherein at least one of R17 to R21 represents an alicyclic hydrocarbon group and one of R19 and R21 represents a straight chain or branched alkyl group having from 1 to 4 carbon atoms or an alicyclic hydrocarbon group; R22 to R25 each independently represents a straight chain or branched alkyl group having from 1 to 4 carbon atoms or an alicyclic hydrocarbon group, wherein at least one of R22 to R25 represents an alicyclic hydrocarbon group and R23 and R24 may be bonded to each other to form a ring: 
wherein R11xe2x80x2 and R12 xe2x80x2 each independently represents a hydrogen atom, a cyano group, a halogen atom or an alkyl group which may have a substituent; Zxe2x80x2 represents an atomic group for forming an alicyclic structure containing the two carbon atoms (Cxe2x80x94C), which may have a substituent.
(3) The positive resist composition according to item (2), wherein Zxe2x80x2 of the formula (II) represents an atomic group for forming a bridged alicyclic structure containing the two carbon atoms (Cxe2x80x94C), which may have a substituent.
(4) The positive resist composition according to item (2), wherein the formula (II) is one of formulae (II-A) and (II-B); 
wherein R13xe2x80x2 to R16 xe2x80x2 each independently represents a hydrogen atom, a halogen atom, a cyano group, xe2x80x94COOH, xe2x80x94COOR5, a group of being decomposed by the action of an acid, xe2x80x94C(xe2x95x90O)xe2x80x94X-Axe2x80x2-R17xe2x80x2, or an alkyl or cyclic hydrocarbon group which may have a substituent; R5 represents an alkyl or cyclic hydrocarbon group which may have a substituent, or a xe2x80x94Y group below; X represents an oxygen atom, a sulfur atom, xe2x80x94NHxe2x80x94, xe2x80x94NHSO2xe2x80x94, or xe2x80x94NHSO2NHxe2x80x94; Axe2x80x2 represents a single bond or a divalent linkage group; n represents 0 or 1; R17 xe2x80x2 represents xe2x80x94COOH, xe2x80x94COOR5, xe2x80x94CN, a hydroxy group, an alkoxy group which may have a substituent, xe2x80x94COxe2x80x94NHxe2x80x94R6, xe2x80x94COxe2x80x94NHxe2x80x94SO2xe2x80x94R6, or a xe2x80x94Y group below; R6 represents an alkyl or cyclic hydrocarbon group which may have a substituent; and at least two of R13xe2x80x2 to R16xe2x80x2 may be bonded to each other to form a ring: 
wherein R21xe2x80x2 to R30xe2x80x2 each independently represents a hydrogen or an alkyl group which may have a substituent; a and b each represents 1 or 2.
(5) The positive resist composition according to item (2), wherein the repeating unit having the partial structure represented by the formula (pI) to (pVI), is a repeating unit represented by formula (pA): 
wherein R represents a hydrogen atom, a halogen atom, a substituted or unsubstituted, straight chain or branched alkyl group having from 1 to 4 carbon atoms; each of plural R is the same or different; A represents a single bond or, an alkylene group, a substituted alkylene group, an ether group, a thioether group, a carbonyl group, an ester group, an amide group, a sulfonamide group, a urethane group, a urea group or a combination thereof; Ra represents one of the groups represented by the formulae (pI) to (pVI).
(6) The positive resist composition according to item (1), wherein the resin (A) further comprises a repeating unit having the lactone structure, represented by formula (IV): 
wherein R1a represents a hydrogen atom or a methyl group; W1 represents a single bond or, an alkylene group, an ether group, a thioether group, a carbonyl group, an ester group or a combination thereof; Ra1, Rb1, Rc1, Rd1 and Re1 each independently represents a hydrogen atom or an alkyl group having from 1 to 4 carbon atoms; m and n each independently represents an integer of from 0 to 3; and m+n is 2 or larger but not larger than 6.
(7) The positive resist composition according to item (1), wherein the resin (A) further comprises a repeating unit having a group represented by one of formulae (V-1) to (V-4): 
wherein R1b to R5b each independently represents a hydrogen atom, an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent or an alkenyl group which may have a substituent, and two of R1b to R5b may be bonded to each other to form a ring.
(8) The positive resist composition according to item (1), wherein the resin (A) further comprises a repeating unit represented by formula (VI): 
wherein A6 represents a single bond or, an alkylene group, a cycloalkylene group, an ether group, a thioether group, a carbonyl group, an ester group or a combination thereof; and R6a represents a hydrogen atom, an alkyl group having from 1 to 4 carbon atoms, a cyano group or a halogen atom.
(9) The positive resist composition according to item (1), wherein the resin (A) further comprises a repeating unit having a group represented by formula (VII): 
wherein R2cto R4ceach independently represents a hydrogen atom or a hydroxy group, and at least one of R2c to R4c represents a hydroxy group.
(10) The positive resist composition according to item (1), wherein the resin (A) further comprises a repeating unit represented by formula (VIII): 
wherein Z2 represents xe2x80x94Oxe2x80x94 or xe2x80x94N(R41); R41 represents a hydrogen atom, a hydroxy group, an alkyl group, a haloalkyl group or xe2x80x94OSO2xe2x80x94R42; and R42 represents an alkyl group, a haloalkyl group, a cycloalkyl group or a camphor residue.
(11) The positive resist composition according to claim 1, wherein the nitrogen-containing compound (C) is a compound represented by formula (Ia): 
wherein Ra represents a hydrogen atom, an alkyl group which may have a substituent, an alkenyl group which may have a substituent or an aryl group which may have a substituent; Rb represents a hydrogen atom, an aryl group which may have a substituent, xe2x80x94C(xe2x95x90O)xe2x80x94Ra or xe2x80x94Nxe2x95x90Nxe2x80x94Ra; and Ra and Rb may be bonded to each other to form a ring.
(12) The positive resist composition according to item (1), wherein the nitrogen-containing compound (C) is a compound represented by formula (II-1): 
wherein R represents a monovalent organic residue having from 1 to 20 carbon atoms.
(13) The positive resist composition according to item (1), wherein the nitrogen-containing compound (C) is a compound represented by formula (II-2): 
wherein R1 to R10, which are the same or different, each represents a hydrogen atom, a hydroxyl group, a halogen atom, a nitro group, a cyano group, an alkyl group, an alkoxy group, a hydroxyalkyl group, a cycloalkyl group or an aryl group.
(14) The positive resist composition according to item (1), wherein the nitrogen-containing compound (C) is used in an amount of from 0.001 to 40% by weight, based on the solid components in the composition.
(15) The positive resist composition according to item (1), which further comprises a low-molecular acid-decomposing compound: having a molecular weight of not higher than 2000; having a group capable of being decomposed by the action of an acid; and increasing the alkali solubility by the action of an acid.
(16) The positive resist composition according to item (1), wherein is a composition for light exposure by a far ultraviolet light having wavelengths of not longer than 220 nm.
(17) The positive resist composition according to item (1), which further comprises (D) a nitrogen-containing basic compound.
(18) The positive resist composition according to item (1), which further comprises (E) a surfactant containing at least one of a fluorine atom and a silicon atom.